Frame for a bicycle



FIG. 1 is a front elevational view of a frame for a bicycle showing my new design;

FIG. 2 is a rear view;

FIG. 3 is a top plan view;

FIG. 4 is a bottom view;

FIG. 5 is a left side view; and,

FIG. 6 is a right side view thereof. 

The ornamental design for a frame for a bicycle, as shown. 